using System;

using System.Collections.Generic;

public class Program

{

    public void Main()

{

    // Sets inputs

    // the double[] input will eventually be the id's of the questions in the database

    double[] input = {123, 893, 4, 12394};

    double toBase = 47;

    string encodedString = encodeString(toBase, input);

    Console.WriteLine(encodedString);

}

​

// Encodes the string

public string encodeString(double baseNum, double[] input)

{

    if (baseNum > 62) {

        throw new Exception("Can't use base higher that 62");

    }

    string finalResult = "";

    List<string> finalEncodedString = new List<string>();

    // Loops through each number in the input list

    foreach (double num in input)

    {

        // sets variables to convert between bases

        double quotient = num;

        double remainder;

        List<double> remainders = new List<double>();

            int i = 0;

            while (quotient >= baseNum)

            {

            // base conversion

            // Example:

            // converting 113 from base 10 to base 13

            // 743 / 13 = 57 r 2

            // 57 / 13 = 4 r 5

            // 4 / 13 = 0 r 4

            // the answer is the remainders read bottom to top, so its 452.

            // this vvv does what I just typed out above

            remainder = quotient % baseNum;

            quotient = Math.Floor(quotient / baseNum);

            remainders.Add(remainder);

            i++;

        }

        remainder = quotient % baseNum;

        remainders.Add(remainder);

        // The remainders are stored in the wrong direction so this reverses them

        List<string> encodedString = new List<string>();

        List<double> reverseRemainders = new List<double>();

        for (var z = remainders.Count - 1; z >= 0; z--)

        {

            reverseRemainders.Add(remainders[z]);

        }

        // converts remainders to the baseX versions

        foreach (double r in reverseRemainders)

        {

            int z = Convert.ToInt32(r);

            if (z > 9 && z <= 35) {

                char character = Convert.ToChar(z + 55);

                encodedString.Add(character.ToString());

            }

            else if (z >= 36 && z < 62)

            {

                char character = Convert.ToChar(z + 61);

                encodedString.Add(character.ToString());

            }

            else if (z <= 9)

            {

                encodedString.Add(r.ToString());

            }

        }

        // adds all strings together

        string result = String.Join("", encodedString);

        finalEncodedString.Add(result);

        finalResult = String.Join(",", finalEncodedString);

    }

    return finalResult;

}

}